Current interrupting system



May 2, 1939. J. J. TAYLOR 2,156,410

CURRENT INTERRUPTING SYSTEM Filed Jan. 11, 1937 Jrame J 7232b).

Patented May 2, 1939 UNITED STATES iPA'lEhl'l orrlcs 12 Claims.

The present invention relates to electric switches or contactors particularly adapted for use in inductive circuits, and in parti ular provides aswitch or contactor and method utilizing auxiliary contact structure disposed to limit the inductive voltage which is generated by the interruption of an inductive circuit.

An illustrative application of the improved method and construction of the present invention is in connection with the control of large direct current solenoids, such, for example, as are used to open and close oil circuit breakers and other relatively heavy switching equipment. In such application, as will be appreciated, the contacts of the control switch, or, as it is hereinafter referred. to, the contactor, are disposed in the circuit of the solenoid, and a closing movement of the circuit breaker or other switching equipment is effected by closing the contactor, thereby energizing the solenoid. Due to the highly inductive character thereof results in the produc tion of very high inductive voltage, of the order of ten times the normal solenoid operating voltage. This high inductive voltage is impressed across the contactor contacts, solenoid winding, wiring, and associated equipment, causing undue insulation and other strains, and resulting in a destructive are between the contacts.

The magnitude of this inductive voltage, as will be appreciated, depends upon the speed with which the interruption of the solenoid circuit occurs, so that, with a View to reducing the inductive voltage, a relatively slow break is desirable. On the other hand, the injury to the con tacts is determined as much by the duration as by the intensity of the are, so that from the standpoint of the contacts, a rapid dissipation of the arc is desirable.

Various arrangements have been proposed heretofore with a view to limiting the inductive voltage during a breaking action, a represtntative one of which is a so-called teaser or third contact. Difficulties have arisen in connection with the previously proposed arrangements, of

which the present applicant is aware, however,

because the secondary are which is drawn between the auxiliary or teaser contact and one of the main contacts, is usually unstable and is blown out, is blown against the wall of the arc so chute, or causes a short circuit of the power supply, any one of which results is seriously detrimental.

In the practice of the present invention, the just noted difficulties as well as others are effecss tivelyovercome by providing the contactor with one or more pairs of auxiliary contacts which are connected in shunt relation to the coil of the solenoid or other inductive element to be controlled by the contactor, and which are disposed to have an arc struck between them as an inci- 5 dent to an opening movement of the contactors, thereby providing a local discharge circuit for the energy stored within the solenoid. The primary arc is made to transfer from the main contacts to the auxiliary contacts, across which a 10 secondary arc is struck, thus minimizing the injury to the main contacts, and, by properly spacing the auxiliary contacts, a relatively slow break is assured thus minimizing the magnitude of the induced voltage. 15

In the preferred embodiment of the invention, the auxiliary contacts, which include at least one pair, are formed of iron or other magnetic and conductive material, and project through the opposite walls of the arc chute associated with the contactor to positions in which the inner ends thereof are in slightly spaced relation. The positioning of the electrodes, moreover, is preferably such that the arc drawn between them. lies parallel to the direction of the magnetic: field of 25 the blowout coil of the contactor, so that such are is not only free from any motor action from the blowout field but is stabilized by it. The positioning is also preferably such that the auxiliary electrodes constitute a part of the magnetic cir- 30 cult of the blowout coil, thus increasing the efiective blowout field and increasing the rate at which the primary are drawn between the main electrode is blown to a position between the auxiliary electrodes. Preferably also the connections for the contactor are such that the blowout coil is included in the local circuit comprising the auxiliary electrodes and the solenoid to be controlled. With this relation, the blowout field persists as long as the auxiliary arc persists and 0 is therefore available to immediately extinguish any are which may be re-struck between the main contacts during the opening operation.

In one modified embodiment of the present invention, the above mentioned single pair of aux- 45 iliary electrodes are replaced by a plurality of pairs of similarly disposed electrodes, all of which are disposed to be connected in series in the previously mentioned local circuit. In an additional embodiment of the invention, the auxiliary electrodes are replaced by an evacuated mercury tube, having a pool of mercury adjacent one end and forming one electrode and a second electrode constituting a metallic disc disposed in the spaced relation to the pool.

The two electrodes of the tube are disposed in parallel relation to the solenoid or other inductive element to be controlled and the inductive voltage which develops in the opening movement of the contactor causes an arc to be struck in the tube of lower resistance than that of the are between the primary electrode. Upon the striking of this secondary arc, the primary arc is extinguished, and the secondary arc persists until the energy which is stored in the solenoid is substantially dissipated.

With the above as well as: other considerations in View, objects of the present invention are to provide an improved switch or contactor construction embodying means to limit the inductive voltage to which the circuit is subjected when used in inductive circuits, and to prolong the life of the main contactor structure; to provide such a structure embodying a pair of auxiliary electrodes disposed to be connected in parallel with the inductive portion of the circuit being controlled, and to which the primary are initially drawn between the main electrodes in an opening movement of the contactor will transfer; to provide such construction in which the auxiliary electrodes are so positioned with relation to the contactor structure that the secondary arc drawn between them is not subject to motor action from the blowout field of the usual contactor blowout coil; to provide such a construction in which the auxiliary electrodes constitute a part of the magnetic circuit of the blowout coil; to provide such a construction in which the contactor connections are such that the blowout coil is included in the local circuit comprising the inductive part of the circuit to be controlled and the auxiliary electrodes, so that the blowout field persists as long as the secondary arc persists; to provide such a construction in which the auxiliary electrode includes a pair of electrode members which project through the side walls of the arc chute of a contactor structure; to provide such a construction in which the auxiliary electrodes consist of a plurality of pairs of electrodes which project through the walls of the contactor arc chute and are disposed to be connected in series circuit relation to each other; to provide such a construction in which the auxiliary electrode structure, includes, for example, an evacuated mercury tube which may be positioned remotely from the contactor structure; and to provide an improved method which may be practiced with the above improved structure.

With the above and others, as well as more specific, objects in view, which appear in the following description and in the appended claims, preferred but illustrative embodiments of the invention are shown in the accompanying drawing throughout which corresponding reference characters are used to designate corresponding parts and in which:

Figure 1 is a general view in elevation of a conventional contactor modified to embody the present invention;

Fig. 2 is a view in front elevation of the structure shown in Fig, 1;

Fig. 3 is a diagrammatic view of the circuit connections between the main and auxiliary contacts of the improved contactor;

Fig. 4 is a fragmentary view illustrating a modified auxiliary electrode arrangement;

Fig. 5 is a diagrammatic view illustrating the preferred circuit connection used with the construction in Fig. 4; and

Fig. 6 is a diagrammatic view of a further modified embodiment of the present invention.

Referring first to Figs. 1 and 2, it will be appreciated from a complete understanding of the present invention that the auxiliary electrode structure thereof may be embodied in contactor constructions of widely differing types, and the illustration thereof in connection with a particular contactor structure is to be regarded in an illustrative and not in a limiting sense. In the illustrated arrangement, the contactor may comprise an operating coil it, suitably connected to the contactor base l2 by a bracket I4. The armature !6 of the contactor, which carries the moving contact l B, is suitably pivoted as by a pin Ell to a support 24 which may form a part of the previously mentioned bracket M. In the energized condition of the coil E8, the armature i6 is held in the illustrated position, in which it is disposed in slightly spaced relation below the end of the solenoid core 26. The moving contact I8 is electrically connected to one terminal 28 of the contactor through the pigtail 3!]. The stationary contact 32 of the contactor in turn is electrically connected to the other terminal 34 of the contactor. The connecting structure may be conventional and accordingly, is not illustrated in Fig. l in order to simplify the drawing. In accordance with conventional practice the contactor is provided with an arc chute 36 which substantially encloses the moving and stationary contacts 88 and 32, as well as a blowout coil 3B. The are chute 36 may also include an interior bafile 4B, which protects the blowout coil 38 from any are which may be between the main contacts l8 and 32 during an opening movement of the contactor.

Considering now the auxiliary electrode structure, a pair of conducting electrodes 42 and 44 are projected through respectively opposite side walls 31 of the arc chute 38, and may as illustrated be provided with inner and outer lock nuts 46 in order to adjust the spacing within the arc chute between the inner ends thereof. The electrodes 42 and 44 may be formed of any of a wide variety of conducting materials, the preferred materials being iron, carbon, and tungsten, because of the special characteristics thereof.

As clearly appears in Figs. 1 and 2, the positioning of the auxiliary electrodes 42 and 44 is such that these electrodes lie in the magnetic circuit of the blowout coil 38 so that, if these electrodes are formed of magnetizable material, the elfective blowout field for a given blowout coil is increased. As also clearly appears in Figs. 1 and 2, anarc drawn between the inner ends of the auxiliary electrodes 42 and M lies parallel to the direction of the magnetic field of the blowout coil 38 and is thus not subjected to any motor action from such blowout field.

Referring particularly to Fig. 3, the auxiliary electrodes 42 and 44 are connected in a local circuit which includes the blowout coil 38 as well as the inductive load element 50 which may represent, for example, the solenoid of an oil circuit breaker.

The operation as a whole of the device may be described as follows. During normal operation of the contactor, when the contactor coil [0 is energized, the main contacts l8 and 32 are retained in the closed position, and connect the solenoid or other inductive element 59 to the power source represented by the plus and minus signs. Under these. conditions it will be appreciated that no arc is drawn between the auxiliary electrodes 42 and 44. When the contactor coil H) is de-energized, with a view to de-energizing the inductive load element 50, the contacts 32 and I8 are relatively rapidly separated, usually by an opening spring (not shown).

Due to the continuous supply of energy from the external power source and due to the energy stored within the load element 50, the initial opening movement of the main contacts l8 and 32 results in the production of a primary are be tween these electrodes. This primary arc, as will be appreciated, extends transversely to the field of the blowout coil 38 and is accordingly subjected to the usual motor action which serves to increase its length and ultimately, in accordance with conventional practice, to extinguish it. The motion of the primary arc, caused by the blowout field, forces this primary arc to traverse the space between the auxiliary electrodes 42 and 44, ionizing the air between these electrodes, and resulting in the striking of a secondary arc between these electrodes. This secondary arc, as previously noted, extends parallel to the direction of the blowout field and consequently is fixed and stabilized by the blowout field; Accordingly, the secondary arc being of shorter length and lower resistance than the primary arc, the energy in the circuit transfers from the primary arc to the secondary arc, extinguishing the primary arc, This extinguishment of the primary arc occurs at the expiration of a very short interval following the initial opening movement of the main contacts l8 and 32, thus minimizing any injury thereto, or to the arc chute 39 or the baffle 40.

Following the opening of the main contacts l8 and 32 and the extinguishment of the primary arc, the contactor is isolated from the external source of supply and the only remaining source of supply for the secondary arc is constituted by the element 59. As soon, accordingly, as the energy stored within the element is dissipated secondary arc, extinguishing the primary arc. fails, thus completing the contactor opening operation. Until such a time as the secondary arc fails, however, the blowout coil 38 remains the secondary arc circuit and is effective to maintain a blowout field throughout the entire arc chute structure. The existence of this continuous blowout field effectively serves to extinguish any primary are which may be struck between the main contacts l 8 and 32, or between a main and an auxiliary contact.

The contactor action is one, accordingly, in which the arc between the primary contacts are rapidly extinguished, thereby minimizing injury to these elements; and in which the energy stored within the inductive load element is permitted to dissipate relatively slowly, thus minimizing the inductive voltage thereof. In practice, utilizing contactors in circuits in which the operating voltage ior the inductive load element is of the order of 100 volts, it is found that the auxiliary electrode structure of the present invention permits the above described rapid elimination of the primary arc, and at the same time limits the inductive voltage to a value less than double the just stated operating voltage. In the absence of the auxiliary electrode structure, on the other hand, the inductive voltage may in practice be expected to reach a peak value of 809 to 2500 volts. In addition to thus substantially improving the contactor operation, it will be noted that the auxiliary electrode structure may be very economically applied to existing contactor structures with only the alteration that is involved in inserting the two electrodes through the side walls of the arc chute and inproviding the previously described circuit connections therefor.

In the alternative embodiment of the invention shown in Figs. 4 and 5, the single pair of auxiliary electrodes 42 and 36 described above are replaced by a plurality of pairs of auxiliary electrodes 42a and 46a, the individual electrodes of each pair of which may project through the side walls of the arc chute in the manner described above. The individual pairs of electrodes are preferably disposed in generally circular relation and so posiiioned that the primary arc struck between the main contacts la and 32a is caused to sweep between each individual pair, thus ionizing the air between them and resulting in a substantially immediate striking of a secondary arc between the electrodes of each pair. The circuit arrangement may duplicate that described with reference to Fig. 3 with the exception that all of the pairs of auxiliary electrodes are connected together in series circuit relation. Alternatively, as shown in Fig. 5, the auxiliary contacts may be disposed in parallel with the main contacts rather than in parallel with the element 50a. An advantage of the arrangement of Figs. 4 and 5 is that by breaking the secondary are up into a series of secondary arcs, a greater total arc length with consequently a greater total are resistance may be provided than in the case of the arrangement of Figs. 1, 2 and 3. The greater total arc resistances as will be appreciated increases the rate at which the energy stored in the inductive load element is dissipated and consequently decreases the period required for the complete opening operation of the contactor. The use of a suitable number of secondary electrodes in series circuit relationship, results in the extinction of the secondary arcs even when a constant potential is being applied across them. A multiple electrode arrangement is, therefore, of advantage in circuits in which the load element contains sources of electric potential separate and in addition to the stored inductive energy of a magnetic field.

In the remaining embodiment of the invention shown in Fig. 6, the structure is adapted for use in instances where the inductive load element is located relatively remotely from the contactor structure and in which it is desired to avoid the running of the auxiliary electrode connections entirely from the contactor to the inductive load element. In the arrangement in question, the auxiliary electrode structure comprises a partially evacuated tube 60 which may contain an inert gas such as neon at a pressure of, for example 5 m. m., and which includes at the base thereof, a pool of mercury 62. The other terminal 56 may constitute a relatively flat metallic disc. The terminals constituted by the pool 62 and the metallic disc 66 are suitably connected in parallel relation to the inductive load element 58b by the circuit conductors 64 and 58.

In operation, an opening movement of the main contacts I8b and 32b draws a primary are between them which primary arc, as in the previous case, is subject to the field of the blowout coil 38b. The opening movement also initiates a reduction in the current flowing in the inductive load element 58b which change in current tends to produce a relatively high inductive voltage which is applied between the terminals t5 and 62 as well as between the contacts I82) and 32b. The design of the tube Gil is such that this inductive voltage is high enough to cause an arc to be struck between the electrodes 62 and 6B, which arc is lower in resistance than the now lengthened primary arc. The primary arc is, accordingly, extinguished as in the previous instance, and the remaining energy stored within the inductive load element 5% is dissipated in the secondary arc.

Although specific embodiments of the present invention have been described in detail, it will be appreciated that various modifications in the form, number, and arrangement of parts and various changes in the disclosed method, may be made within the spirit and scope thereof.

What is claimed is:

1. In a switch, the combination of a pair of separable main contacts in the circuit of an inductive load element and between which a primary arc may be drawn when they are separated, means providing a blowout field for said primary are, and auxiliary contact means electrically connected to said circuit between which a secondary arc may form as a consequence of said primary arc, said auxiliary contact means being so disposed that said secondary arc runs substantially parallel to the direction of said blowout field.

2. In a switch, the combination of a pair of separable main contacts in the circuit of an inductive load element and between which a primary arc may be drawn when they are separated, a blowout coil associated with said main contacts to provide a blowout field for said primary arc, auxiliary contact means electrically connected to said circuit between which a secondary arc may form as a consequence of said primary arc, and means supporting said auxiliary contact means in the magnetic circuit of the blowout coil and so that said secondary arc runs substantially parallel to the direction of said blowout field.

3. In a switch, the combination of a pair of separable main contacts in the circuit of an inductive load element and between which a primary arc may be drawn when they are separated, an arc chute for said primary are, means providing a blowout field to cause said primary arc to move through said chute, and a pair of auxiliary contacts electrically connected to said circuit projecting inwardly from the side walls of said chute and disposed in the path of movement of said primary arc, said auxiliary contacts being so disposed that a secondary arc drawn between them lies substantially parallel to the direction of said blowout field.

4. In a switch, the combination of a pair of separable main contacts between which a primary arc may be drawn when they are separated, and included in the circuit of an inductive load element, means providing a blowout field for said primary are, a pair of auxiliary contacts supported in said switch and disposed so that a secondary are drawn between them runs substantially parallel to the direction of said blowout field, and circuit connections for connecting said auxiliary contacts in parallel relation to said load element.

5. In a switch, the combination of a pair of separable main contacts in the circuit of an inductive load element and between which a primary arc may be drawn when they are separated and included in the circuit of an inductive load element, a blowout coil for providing a blowout field for said primary arc, a pair of auxiliary contacts to which said primary arc may transfer and form a secondary arc, means supporting said contacts in said switch structure so that said secondary arc runs substantially parallel to the direction of said blowout field, and circuit connections for electrically connecting said auxiliary contacts in parallel with said blowout coil and with said inductive load element.

6. In a switch, the combination of a pair of separable main contacts adapted for connection in an inductive circuit and between which a main arc may be drawn when they are separated, auxiliary contact means, means electrically connecting said auxiliary contact means to said circuit so that said main arc may transfer away from said main contacts to said auxiliary contactmeans to form a secondary arc, means providing a blowout field to effect said transfer, said connecting means being so arranged that said blowout means is energized by the current in the secondary arc and so maintains said blowout field as long as said secondary arc persists, and said auxiliary contact means being so positioned that said secondary arc lies within and runs substantially parallel to the direction of said blowout field.

7. The combination with a pair of terminals in an inductive circuit and between which a primary arc may be drawn, of auxiliary terminal means electrically connected to the circuit, means for establishing a magnetic field in motorizing relation to said primary arc to cause the formation of an auxiliary arc across said auxiliary terminals means in which the inductive energy of said circuit may be dissipated, and means supporting said auxiliary terminal means so that said auxiliary arc is in said field but is not motorized thereby.

8. The combination with a pair of terminals in an inductive circuit and between which a primary arc may be drawn, of auxiliary terminal means electrically connected to the circuit, means for establishing a magnetic field in motorizing relation to said primary arc to cause the formation of an auxiliary arc across said auxiliary terminal means in which the inductive energy of said circuit may be dissipated, and means supporting said auxiliary terminal means so that said auxiliary arc is in said field and runs in a direction substantially parallel to the direction of said field.

9. The combination with a pair of terminals in an inductive circuit and between which a primary arc may be drawn, of auxiliary terminal means electrically connected to the circuit, means for establishing a magnetic field in motorizing relation to said primary arc to cause the primary arc to sweep over a predetermined area and cause the formation of an auxiliary arc across said auxiliary terminal means in which the inductive energy of the circuit may be dissipated, and means supporting said auxiliary terminal means so that said auxiliary arc passes transversely through said area and is not motorized by said field.

10. The combination with a pair of terminals in the circuit of an inductive load element and between which. a primary arc may be drawn, of auxiliary terminal means, means electrically connecting said auxiliary terminal means in a secondary circuit which includes said load element but does not include said terminals, means excited by current in said secondary circuit for establishing a magnetic field in motorizing relation to said primary arc to cause the formation of an auxiliary arc across said auxiliary terminal means, and means supporting said auxiliary terminal means so that said auxiliary arc is in said field but is not motorized thereby.

11. The combination with a pair of terminals in the circuit of an inductive load element and between which a primary arc may be drawn, of auxiliary terminal means, means electrically connecting said auxiliary terminal means in a secondary circuit which includes said load element but does not include said terminals, means excited by current in said secondary circuit for establishing a magnetic field in motorizing relation to said primary arc to cause the formation of an auxiliary arc across said auxiliary terminal means, and means supporting said auxiliary terminal means so that said auxiliary arc is in said field and runs in a direction substantially parallel to the direction of said field.

12. The combination with a pair of terminals in an inductive circuit and between which a primary arc may be drawn, of a plurality of pairs of auxiliary terminals, means electrically conmeeting said pairs of auxiliary terminals in series circuit relation with each other and to said inductive circuit, means for establishing a magnetic field in motorizing relation to said primary arc to cause the formation of auxiliary arcs across said pairs of auxiliary terminals and in which the inductive energy of said circuit may be dissipa ted, and means supporting said auxiliary terminals so that said auxiliary arcs are in said field but are not motorized thereby.

JEROME J. TAYLOR.

7 CERTIFICATE OF CORRECTION. Patent No. 2,156,L l0. v May 2, 1959.

JEROME J.- TAYLOR,

- It is hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 3, first column, line 1 2, strike out. the words and period "secondary arc, extinguishing the primary are. and insert instead to a predetermined degree, the secondary arc; andxthat the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 27th day of June, A. D. 1959.

Henry Van Arsdale (Seal). Acting Commissioner of Patents.

' Patent Office.

CERTIFICATE OF CORRECTION. Patent No. 2,156,LL10. May 2, 1959.

' JEROME J.- TAYLOR,

-It is hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 5, first column,- line 1+2, strike out the words and period "secondary arc, extinguishing the primary arc. and insert instead to a predetermined degree the secondary arc; andrthat the said Letters Patent should be read with this correction therein thatthe same" may conform to the record of the case in the Signed and sealed. this 27th day of June, A; D. 1959.

Henry Van Arsdale (Seal) I Acting Commissioner of Patents. 

